JPS6365931B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photosensitive resin composition for printing plates, and particularly to a photosensitive resin composition for flexographic printing plates for cardboard boxes, which require printing plates with a large relief depth. An object of the present invention is to provide a storage-stable photosensitive resin composition for flexographic printing plates. As is well known, rubber plates have traditionally been used in flexo printing, which is used to print packaging materials such as film, cardboard, and kraft paper.
Recently, with the demand from the industry to simplify the plate-making process and save labor, there has been a rapid increase in the use of photopolymer plates instead of rubber plates, and photopolymer plates are already being used in some areas. I'm starting. The present inventors have already conducted extensive research in order to obtain a photosensitive resin suitable for flexographic printing plates that has low hardness and high strength, and have found that active hydrogen that can react with isocyanate groups in the urethane-modified acrylate contained in the urethane-modified acrylate resin 2 groups in the molecule
By using polyalkylene glycol (A) and aromatic oligoester (B) as compounds having more than 100% polyalkylene glycol, a photosensitive urethane-modified acrylate resin composition that can be developed with an aqueous solvent and has excellent physical properties is now available. proposed (patent application 1972-58106)
issue). In addition, urethane-modified acrylate (),
Copolymerizable monomer () and photoinitiator ()
We have proposed a method for obtaining a printing plate in which shoulder formation is easy and there is no cupping phenomenon using a photosensitive urethane-modified acrylate resin composition (Japanese Patent Application No. 34708/1983). However, in the above resin composition, when a benzoin ether compound is used as a photopolymerization initiator () and a tertiary amine compound is used as a photopolymerization initiation aid, the photocuring rate gradually increases with time; It was found that it had the disadvantage of eventually turning into a gel, and was not sufficient in terms of storage stability. Generally, it is said that it is effective to add a thermal polymerization inhibitor such as hydroquinone or P-benzoquinone to prevent dark reactions and gelation of the resin composition during storage. It has also been found at the same time that in a resin composition using a combination of a benzoin ether compound and a tertiary amine compound, gelation during storage cannot be prevented by adding a thermal polymerization inhibitor. The present inventors conducted extensive research to solve these problems, and surprisingly found that by adding a small amount of water to the composition, the storage stability was significantly improved and the photocuring speed was decreased. The present invention was achieved by discovering the fact that changes over time are extremely reduced and gelation during storage is also suppressed. That is, in the present invention, 0.01 to 10 parts by weight of a benzoin ether compound () and 0.05 to 10 parts by weight of a tertiary amine compound () are added to 100 parts by weight of a urethane-modified acrylate resin consisting of a urethane-modified acrylate () and a copolymerizable monomer (). Parts by weight and water 0.05
This is a storage-stabilized photosensitive resin composition for flexographic printing plates, in which ~1.0 part by weight is added. In the present invention, the urethane-modified acrylate () is a polymer having at least two acryloyloxy groups and/or methacryloyloxy groups at the end of the molecule and at least four urethane bonds within the molecule, and is a urethane-modified acrylate resin. is a curable resin made by blending this urethane-modified acrylate with a copolymerizable monomer. The above urethane-modified acrylate () has 2 active hydrogen groups in its molecule that can react with isocyanate groups.
It is derived from a compound having 1 or more organic diisocyanates and an acrylate compound containing an alcoholic hydroxyl group. As the compound having two or more active hydrogen groups in the molecule that can react with isocyanate groups, polyalkylene glycol or aromatic oligoester is used. In the present invention, in particular, the urethane-modified acrylate () consists of a polyalkylene glycol (A) with a molecular weight of 400 to 5,000 and an aromatic oligoester (B) with a molecular weight of 200 to 2,000, and the molar ratio of (A)/(B) is 4. /1～
in the range of 1/4, and (A)/(B) is 1.0 in weight ratio
It is desirable to use a compound having two or more active hydrogen groups capable of reacting with an isocyanate group in its molecule, or a compound derived from an organic diisocyanate and an alcoholic hydroxyl group-containing (meth)acrylate compound. Molecular weight for polyalkylene glycol (A)
400-5000 polyethylene glycol, molecular weight 400
~5000 polypropylene glycol, molecular weight 500
Polytetramethylene glycol, molecular weight ~3000
500-5000 ethylene glycol-propylene glycol block copolymer, molecular weight 500-
3000 ethylene glycol-tetramethylene glycol copolymer, propylene oxide or/and ethylene oxide adduct of glycerin with molecular weight 400-3000, propylene oxide or/and ethylene oxide adduct of trimethylolpropane with molecular weight 400-3000, hydrogen with molecular weight 400-2000 Examples include propylene oxide adducts of bisphenol (A). In addition, if necessary, ethylene glycol, propylene glycol, 1,3-propanediol, diethylene glycol, dipropylene glycol,
Neopentyl glycol, dichloroneopentyl glycol, dibromoneopentyl glycol,
1,4-butanediol, 1,4-butenediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,4-
It is also possible to partially use low molecular weight polyhydric alcohols such as cyclohexanedimethanol, 1,4-cyclohexanediol, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. In particular, it is preferable to partially use polytetramethylene glycol and other alkylene glycols having a molecular weight of 500 to 3,000. Molecular weight in polyalkylene glycol (A): 500
The proportion of polytetramethylene glycol in ~3000 is
The proportion of other polyalkylene glycols is preferably 80 to 20 mol%. Aromatic oligoester (B) is an oligoester of orthophthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, etc. obtained by the reaction of aromatic polybasic acids and their derivatives with polyhydric alcohols, especially terephthalic acid. Oligoesters from and derivatives thereof are preferred. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, 1,
3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,4-butenediol, 1,6-hexanediol, 2,2,4
-trimethyl-1,3-pentanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adduct of bisphenol (A), glycerin,
Examples include trimethylolpropane and pentaerythritol. Examples of methods for producing aromatic oligoester (B) include direct esterification of aromatic polybasic acid and polyhydric alcohol, transesterification of aromatic polybasic acid alkyl ester and polyhydric alcohol, polyethylene terephthalate, There are methods such as depolymerizing polybutylene terephthalate with polyhydric alcohol, and known catalysts can be used as necessary during production. The aromatic oligoester (B) preferably has an acid value of 20 or less and a molecular weight of 200 to 2,000. If the acid value exceeds 20, the solubility will deteriorate and the transparency of the urethane-modified acrylate resin will be lost, and if the molecular weight exceeds 2000, the viscosity of the urethane-modified acrylate resin will become extremely high, making it difficult to handle. cause harm. As an organic diisocyanate compound, 2,4-
These organic diisocyanate compounds include tolylene diisocyanate, 2,6-tolylene diisocyanate, metaphenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, bis(isocyanatomethyl)cyclohexane, and isophorone diisocyanate, and these organic diisocyanate compounds can be used alone or in combination. used. To obtain the urethane-modified acrylate () used in the present invention, first, polyalkylene glycol
(A) and aromatic oligoester (B) are reacted with an organic diisocyanate compound to obtain a urethane prepolymer containing a terminal isocyanate group, and then this urethane prepolymer containing a terminal isocyanate group is reacted with an acrylate or methacrylate containing an alcoholic hydroxyl group. A urethane-modified acrylate is produced by this process. The method for producing a urethane prepolymer containing terminal isocyanate groups is as follows: (1) Polyalkylene glycol
(A) and aromatic oligoester (B) and an organic diisocyanate compound (OH group/COOH group)/
Either (2) polyalkylene glycol (A) (or aromatic oligoester (B)) and organic diisocyanate compound are reacted at a ratio of NCO group < 1 (equivalent ratio), or (OH group + COOH group)/NCO group. <1
(Equivalent ratio) of aromatic oligoester (B) (or polyalkylene glycol (A)) to the reaction product obtained by reacting with the remaining isocyanate groups (OH group + COOH group) / NCO group < 1 (equivalent ratio) There is a method of reacting at a ratio of . The reaction ratio of polyalkylene glycol (A) and aromatic oligoester (B) with organic diisocyanate compound is (OH group + COOH group)/NCO group <1
(equivalent ratio), preferably 0.3 to 0.8. Furthermore, the ratio of polyalkylene glycol (A) to aromatic oligoester (B) is in the range of 4/1 to 1/4 in molar ratio, preferably 3/1 to 1/2, and in weight ratio.
(A)/(B)>1. If the molar ratio of (A)/(B) exceeds 4/1, the effect of the aromatic oligoester will not be exhibited and only a printing plate with low strength will be obtained. On the other hand (A)/
If the molar ratio of (B) is less than 1/4 and the weight ratio is less than 1.0, the viscosity of the urethane-modified acrylate resin will increase, making it difficult to handle, and it may be necessary to wash out the unexposed areas using a hydrogen solvent. It will be extremely difficult. The above reaction is carried out without a solvent or using a solvent inert to isocyanate groups such as styrene, vinyltoluene, ethyl acrylate, methyl methacrylate, benzene, toluene, and methylene chloride. Reaction temperature is 20~120℃, especially 50℃~100℃
It is desirable to do so. If necessary, known catalysts such as organic tin compounds and organic amines can also be used. Examples of the alcoholic hydroxyl group-containing acrylate or methacrylate that can react with the terminal isocyanate group-containing urethane prepolymer include ethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate, and 1,3-
propanediol mono(meth)acrylate,
1,3-butanediol mono(meth)acrylate, 1,4-butanediol mono(meth)acrylate, diethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate
Acrylate, mono(meth)acrylate of dihydric alcohol such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, trimethylolethane mono(meth)acrylate, trimethylolethane di(meth)acrylate, trimethylolpropane Mono- and di(meth)acrylates of trihydric alcohols such as mono(meth)acrylate, trimethylolpropane di(meth)acrylate, glycerin mono(meth)acrylate, glycerin di(meth)acrylate, or pentaerythritol di(meth)acrylate , pentaerythritol tri(meth)acrylate, etc.
Examples include di(meth)acrylate and tri(meth)acrylate of alcohols with higher valences. The reaction ratio between the urethane prepolymer containing terminal isocyanate groups and the acrylate or methacrylate containing alcoholic hydroxyl groups is OH group/NCO group ≧
1 (equivalent ratio), preferably 1.05 to 1.3. This reaction is carried out in the solvent used in the first stage reaction or without a solvent, and the reaction temperature is preferably 80°C or lower. In order to inhibit thermal polymerization in the above reaction, it is desirable to use a known thermal polymerization inhibitor such as hydroquinone, hydroquinone monomethyl ether, t-butylcatechol, p-benzoquinone, or phenothiazine. Examples of the copolymerizable monomer () include styrene, vinyltoluene, chlorostyrene, t-butylstyrene, α-methylstyrene, divinylbenzene,
Acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate,
sec-butyl (meth)acrylate, t-butyl (meth)acrylate, α-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)acrylate, n-tridecyl ( meth)acrylate, stearyl(meth)acrylate, ethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate, diethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate
Acrylate, polyethylene glycol mono(meth)acrylate, molecular weight 200-1000, molecular weight
200-1000 polyethylene glycol monomethyl ether mono(meth)acrylate, molecular weight 200
~1000 polypropylene glycol mono(meth)
Acrylate, polypropylene glycol monomethyl ether mono(meth)acrylate with a molecular weight of 200-1000, polyethylene glycol monoethyl ether mono(meth)acrylate with a molecular weight of 200-1000, polypropylene glycol monoethyl ether mono(meth)acrylate with a molecular weight of 200-1000, n -Butoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofuryl (meth)acrylate, glycidyl (meth)acrylate, allyl (meth)acrylate, benzyl (meth)acrylate, tribromophenyl ( meth)acrylate, 2,3-dichloropropyl(meth)acrylate, 3-chloro-
2-hydroxypropyl (meth)acrylate,
N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N-t-butylaminoethyl (meth)acrylate, acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide , ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate
Acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, glycerin di(meth)acrylate, glycerin tri(meth)acrylate ) acrylate, trimethylolethane di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene bisacrylamide, diallyl phthalate, triallyl isocyanurate , dibutyl fumarate, vinyl acetate, etc., and are selected depending on the purpose. In the photosensitive resin composition for flexographic printing plates of the present invention, the blending ratio of urethane-modified acrylate () and copolymerizable monomer () is from 90:10 to 90:10 by weight.
20:80, preferably 80:20 to 40:60. The photosensitive resin composition for flexographic printing plates of the present invention includes the above urethane-modified acrylate resin, a benzoin ether compound as a photopolymerization initiator (), and a third
It is obtained by adding a grade amine compound () and water. Examples of benzoin ether compounds include benzoin methyl ether, benzoin ethyl ether, benzoin-iso-propyl ether, benzoin-n-propyl ether, benzoin-
Examples include n-butyl ether. The amount added is 0.01 to 10 parts by weight, preferably 0.05 to 3 parts by weight, per 100 parts by weight of the urethane-modified acrylate resin. As the photopolymerization initiator (), it is also possible to use the above benzoin ether compound and other photopolymerization initiators together. Such compounds include benzoin, diacetyl, benzyl, benzophenone, acetophenone, butyroin, trioin,
Fluorescene, eosin, erythrosine, α-mercaptobenzothiazole, α-mercaptobenzoxazole, diphenyl sulfide, dibenzyl disulfide, tetramethylthiuram monosulfide, tetramethylthiuram disulfide,
Examples include 9,10-anthraquinone and 1,4-toftoquinone. Examples of the tertiary amine compound () include trimethylamine, triethylamine, tri-n-
Butylamine, triethylenetetramine, tetraethylenepentamine, triethanolamine, dimethylaminoethanol, diethylaminoethanol, di-n-butylaminoethanol, N-ethyldiethanolamine, N-n-butyldiethanolamine, N,N-dimethylaminoethyl ( Examples include amine compounds such as meth)acrylate and N,N-diethylaminoethyl (meth)acrylate, but preferably tertiary amines that can be copolymerized with urethane-modified acrylate () or/and copolymerizable monomer () It is preferable to use compounds such as N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and the like. The amount of the tertiary amine added is 0.05 to 10 parts by weight per 100 parts by weight of the urethane-modified acrylate resin.
Preferably it is 0.1 to 5 parts by weight. The amount of water added in the present invention is 0.01 to 1.0 parts by weight per 100 parts by weight of the urethane-modified acrylate resin.
Preferably it is 0.05 to 0.5 part by weight. If it is less than 0.01, the effect of improving storage stability will be small, and if it exceeds 1.0 part by weight, the hardness of the cured product will decrease and the mechanical strength will also decrease, which is not preferable. When curing the photosensitive resin composition for flexographic printing plates of the present invention, examples of light sources used include sunlight, low-pressure mercury lamps, high-pressure mercury lamps, and carbon arc lamps. The photosensitive resin composition for flexographic printing of the present invention can be prepared by exposing a negative film to light using the above light source to form a relief image, and then washing out the unexposed areas using an appropriate solvent. You can get a printed version. As such a solvent, a neutral detergent aqueous solution is suitable. The photosensitive resin composition for flexographic printing plates of the present invention has extremely excellent storage stability, and by taking advantage of this feature, it can be used in coatings, adhesives, vibration damping materials, vibration-proofing materials, coating agents, insulation materials, etc. It can also be used for various purposes such as agents. EXAMPLES Next, Examples will be given to explain the present invention more specifically, but the present invention is of course not limited to these Examples. In the examples, the storage stability test was carried out by covering the photosensitive resin composition in a polyethylene container with aluminum foil to prevent it from being exposed to external light.
The samples were stored in thermostats at 40°C and 40°C, and the presence or absence of gelation and changes in photocuring rate over time were measured.
The photocuring speed was measured by covering the photosensitive resin composition with a polyester film, pouring it onto a glass plate sandwiching a 3 mm thick rubber spacer, and exposing it to ultraviolet light at an intensity of 6000 μw/cm ² or 2000 μw/cm ² for 1 minute. It was determined by measuring the thickness of the cured layer when irradiated. In addition, an ultraviolet intensity meter UVR-365 manufactured by Tokyo Kogaku Kikai Co., Ltd. was used to measure the ultraviolet intensity. Synthesis Example 1 Polypropylene glycol #2000 (molecular weight
1968) 394 g (0.2 mol), 39 g (0.1 mol) of terephthalic acid-dipropylene glycol oligoester (acid value 2.8, molecular weight 390), 70 g (0.4 mol) of 2,4-tolylene diisocyanate, and 0.2 g of dibutyltin dilaurate. 4 at 80℃ using as a catalyst
The reaction was carried out for a period of time to obtain a urethane prepolymer containing terminal isocyanate groups. Next, 29 g (0.22 mol) of ethylene glycol monomethacrylate was charged and reacted at 80° C. for 3 hours to obtain urethane-modified acrylate. 64 parts by weight of the obtained urethane-modified acrylate, 12 parts by weight of phenoxyethyl methacrylate, 12 parts by weight of lauryl methacrylate, and 12 parts by weight of n-butoxyethyl methacrylate were mixed and dissolved to obtain a urethane-modified acrylate resin (A). Example 1 Urethane-modified acrylate resin obtained in Synthesis Example 1
(A) Benzoin ethyl ether per 100 parts by weight
A photosensitive resin composition was obtained by adding and dissolving 0.5 parts by weight and 3 parts by weight of N,N-diethylaminoethyl methacrylate, and various additives were added thereto to examine its storage stability at 25°C. The results are shown in Table 1. 1st
In the table, PHR represents parts by weight based on 100 parts by weight of the urethane-modified acrylate resin (A). Table 1 shows that with conventional thermal polymerization inhibitors, it was not possible to prevent the photocuring rate from changing over time and from gelation during storage, and in the case of P-benzoquinone and phenothiazine, the storage stability deteriorated. on the other hand,
When the water of the present invention is added, the photocuring speed changes.

[Table] The storage stability was significantly improved. Synthesis Example 2 In the same reaction vessel as Synthesis Example 1, add 197 g (0.1 mol) of polypropylene glycol #2000 (molecular weight 1968) and polytetramethylene glycol #2000 (molecular weight 1968).
197 g (0.1 mol) and 70 g (0.4 mol) of 2,4-tolylene diisocyanate were charged and reacted at 80°C for 2 hours using 0.2 g of dibutyltin dilaurate as a catalyst. Value 2.8, molecular weight 390) 39
g (0.1 mol) and reacted at 80° C. for 2 hours to obtain a urethane prepolymer containing terminal isocyanate groups. Next, 0.01g of hydroquinone
29 g (0.22 mol) of ethylene glycol monomethacrylate containing 29% of ethylene glycol was charged and reacted at 80°C for 3 hours to obtain a urethane-modified acrylate. 64 parts by weight of the obtained urethane-modified acrylate, 12 parts by weight of phenoquinethyl methacrylate, 12 parts by weight of lauryl methacrylate, and 12 parts by weight of n-butoxyethyl methacrylate were mixed and dissolved to obtain a urethane-modified acrylate resin (B). Example 2 Urethane-modified acrylate resin obtained in Synthesis Example 2
(B) Benzoin ethyl ether per 100 parts by weight
0.1 part by weight, 0.5 part by weight of benzophenone and N,N-
Three parts by weight of diethylaminoethyl methacrylate was added and dissolved to obtain a photosensitive resin composition, water was added, and the storage stability at 40°C was examined. The result is the second
Shown in the table. Addition of water significantly improved storage stability even at 40°C. Comparative example: Urethane-modified acrylate resin obtained in Synthesis Example 2
(B) Benzoin ethyl ether per 100 parts by weight
0.1 part by weight, 0.5 part by weight of benzophenone and N,N-
Add and dissolve 3 parts by weight of diethylaminoethyl methacrylate to obtain a photosensitive resin composition.Add alcohols, glycols, and carboxylic acids, and then add and dissolve at 40°C.
The storage stability was investigated. The results are shown in Table 3. As is clear from Table 3, these

【table】

[Table] The compound had no effect on storage stabilization.

Claims (1)

[Scope of Claims] 1. To 100 parts by weight of a urethane-modified acrylate resin consisting of a urethane-modified acrylate () and a copolymerizable monomer (), 0.01 to 10 parts by weight of a benzoin ether compound as a photopolymerization initiator () and a third grade amine compound () 0.05 to 10 parts by weight and water
A storage-stabilized photosensitive resin composition for a flexographic printing plate, which contains 0.05 to 1.0 parts by weight. 2 The molecular weight of urethane-modified acrylate ()
It consists of a polyalkylene glycol (A) having a molecular weight of 400 to 5000 and an aromatic oligoester B having a molecular weight of 200 to 2000, the molar ratio of (A)/(B) is in the range of 4/1 to 1/4, and (A) /(B) has 2 active hydrogen groups in the molecule that can react with isocyanate groups with a weight ratio of 1.0 or more.
2. The photosensitive resin composition for a flexographic printing plate according to claim 1, which is a compound derived from an organic diisocyanate and an alcoholic hydroxyl group-containing acrylate compound.